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Antibacterial activity of phytochemicals isolated from Erythrina zeyheri against vancomycin‐resistant enterococci and their combinations with vancomycin
Author(s) -
Sato M.,
Tanaka H.,
OhUchi T.,
Fukai T.,
Etoh H.,
Yamaguchi R.
Publication year - 2004
Publication title -
phytotherapy research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.019
H-Index - 129
eISSN - 1099-1573
pISSN - 0951-418X
DOI - 10.1002/ptr.1556
Subject(s) - staphylococcus aureus , erythrina , minimum inhibitory concentration , antibacterial activity , vancomycin , microbiology and biotechnology , antibacterial agent , potency , methicillin resistant staphylococcus aureus , biology , chemistry , traditional medicine , bacteria , in vitro , antimicrobial , antibiotics , medicine , biochemistry , genetics
Six phytochemicals were isolated from the roots of Erythrina zeyheri (Leguminosae) by repeated silica gel column chromatography using various eluting solvents. Extensive spectroscopic studies revealed that all were isoavonoids. The antibacterial activity of the six compounds against vancomycin‐resistant enterococci (VRE) was estimated by determining the minimum inhibitory concentration (MIC). Of the six isoavonoids, erybraedin A ((6a R , 11a R )‐3,9‐dihydroxy‐4,10‐di( γ , γ ‐dimethylallyl)pterocarpan) exhibited the highest growth inhibitory potency against VRE with an MIC value of 1.56–3.13 µg/mL, followed by eryzerin C ((3 R )‐7,2′,4′‐trihydroxy‐6,8‐di( γ , γ ‐dimethylallyl)isoavan) (MIC 6.25 µg/mL). These compounds also inhibited the growth of methicillin‐resistant Staphylococcus aureus (MRSA) at 3.13–6.25 µg/mL. The antibacterial effects of the two compounds against VRE and MRSA were based on bacteriostatic action. When erybraedin A or eryzerin C was combined with vancomycin, the fractional inhibitory concentration (FIC) index against VRE ranged from 0.5306 to 1.0 and from 0.5153 to 0.75, respectively. The combinations also showed FIC indices of 0.6125–1.0 against MRSA. The results indicate that, depending on the case, both compounds act either synergistically or additively with vancomycin against VRE and MRSA. Erybraedin A and eryzerin C show evidence of being potent phytotherapeutic agents against infections caused by VRE and MRSA. Copyright © 2004 John Wiley & Sons, Ltd.